Technical Field
This invention relates generally to the field of providing control of room temperature. More specifically, this invention relates to remote control of low voltage thermostats used for temperature control in homes and enterprises, using power line communication connections through the low voltage power lines.
Description of the Related Art
It has been found that 45-50% of the energy usage in the home is due to heating and cooling the home. Successful implementation of the Smart Grid for control of home heating and cooling requires communication to the home and to thermostat for control. The system for thermostat control must be able to respond to changes in grid conditions such as energy prices, critical peaks, and other curtailment events and provide control capability for the thermostat over the local area network (LAN), Home area network (HAN) and the internet.
Utilities and service providers are deploying a variety of communication standards and technologies today. Smart Grid information may reach the home through diverse means, e.g. AMI system, cellular, FM radio, Internet, paging, power-line carrier, etc., each being optimal under different circumstances. Within the home, these signals may be received directly by individual end devices or may pass through an energy management system or gateway.
The term USNAP is an acronym for Universal Smart Network Access Port, a simple, cost effective, solution that enables any LAN, HAN or DR (Demand Response) standard, present and future. This standard can be used to communicate with thermostats within the home. By providing industry with a protocol independent modular communication interface (MCI) that connects communication devices to any products that comply with advanced metering infrastructure (AMI) standard, it is possible for manufacturers to produce intelligent and energy aware consumer products, such as thermostats that are able to interact with the Smart Grid.
Currently there are few remote controlled thermostats being used. Some of the new thermostat control products that are USNAP compliant and operate via wireless links are such as Wi-Fi, Z-wave and ZigBee®. The advantage of the USNAP compliance is that the various USNAP compliant modules are replaceable within the thermostat and connect seamlessly to the controller to provide the necessary controllability via the LAN, HAN or internet. FIG. 1 is a block diagram representation 100 of the prior art thermostat 101 with a USNAP enabled replaceable plug-in module 105 that is one of a Wi-Fi or ZigBee® enabled. The display 102 provides the temperature and other program information relevant to the controller. Under normal operation the temperature of the room is displayed. The set of controls 103 allows setting and changing of the temperature of the surroundings of the thermostat 101. A low power supply line 110 combined with a control lead 111 run from the thermostat to the furnace and air conditioning unit. The low voltage power supply typically provides a 24 Volt AC supply to the thermostat or controller from the furnace.
Previously providing data communication connection to appliances that were isolated by step-down or step-up transformers was expensive as special bypass capacitors had to be installed on the transformers to allow data to pass from one side to the other. In the case of thermostat control the thermostat is powered by low voltage generated by stepping down the supply voltage. This has limited the use of the power line communication (PLC) based data communication connections to the thermostat for climatic (temperature) control of the home or enterprise.